A Stranger in His Arms
by Nonnie
Summary: A new case leaves Castle upset, nervous and uncooperative and Kate has to find out why.
1. Chapter 1

Disclaimer – I don't own Castle or any of the characters. Although I will admit wishing I DID own Castle after the picture of NF that was on the website from Comic-Con. He really IS ruggedly handsome!

Kate Beckett winced as her hand slammed into a banister as she took the stairs two at a time, yelling his name. "CASTLE!" Her pace nowhere near matched his. She had never seen Richard Castle move this fast. She thought back quickly to the events that had set this chase in motion. He had visibly paled, but revealed nothing to her, when she'd told him the destination address. His eyes had darted nervously between her and the tony Manhattan building when they'd arrived, but it was one short sentence from Esposito that had sent him barreling up the heavy oak stairs. "The vic's daughter found him."

She could hear his voice above her, wild and strangled with both adrenaline and fear. He was saying a name, but she couldn't make it out…Kara? Tara? "CASTLE!" she called again as she finally reached the landing. The floor beneath her feet was an ornate, elaborate pattern of marble and granite. A round glass and mahogany table was before her, topped with a large bouquet of fresh flowers. She caught just a flicker of his tan overcoat disappear into a room just off the main foyer. She rounded the corner and the scene before her left her speechless.

Arms clothed in a thinly knit ivory sweater circled his neck. His arms around a woman, one at her back, the other pressing her honey blonde braid into his chest. He pressed soft, gentle kisses onto the top of her head, his eyes closed against the gut-wrenching sobs overtaking her slender form. Kate had never felt more uncomfortable – watching as her partner, _her _Castle, consoled this unknown woman.

She turned away, closing her eyes to the quiet reassurances he was offering, "Shh…I'm here. I'm right here, it's okay…"

She glanced at Ryan, who only shrugged, offering no explanation as to this woman's name or position in Richard Castle's life. Esposito leaned into toward his boss' ear. "Zara Chase…she's the victim's daughter – Conrad Chase. 68 years old, major real estate developer. Single GSW to the head. I have no idea what her connection to Castle is."

Kate felt the color drain from her face. Zara….Z…. She shook her head against the thoughts forming in her head. His watch…the one he'd started wearing after his last birthday. He had taken it off one day after an unfortunate run-in with an irritant that left a nasty rash on his arm. She'd picked it up to tease him about the Tag Hauer "knockoff" being the cause of the rash when she noticed the inscription on the back. "Happy Birthday! Love, Z"

The three turned back to the couple to find that Rick had tucked the petite blonde into his side, one arm still around her waist while the other held his cell phone to his ear. She wiped tears from her eyes with the back of her hand and stared down at the lifeless body of her father on the blood stained mahogany wood. "I don't _know_, Mother," Kate heard Castle say "all I know right now is that Conrad is dead and Zara found him."

He must have been content with Martha's answer because he stabbed the disconnect button with his thumb and jammed the phone back into his pocket. "Let's get you out of here," he said gently to Zara, his body never severing contact with hers, breezing past Beckett to lead her back into the foyer.

"Castle," she said his name again, this time through clenched teeth. Who the hell was he to remove her only witness? She stalked after him with Ryan and Esposito hot on her heels. She swung the door to the kitchen open and stepped inside to find Castle pulling out a chair and ordering Zara Chase to sit. "Castle, what the HELL?" she demanded.

Jolted from his thoughts, Rick looked at her with wide eyes. "Beckett?" he said, his tone surprised, as though he'd forgotten he'd arrived on the scene with her. "Yeah, Castle. Remember me? "

His eyes darted between Kate and Zara. "Of course I remember you," he answered nervously, "what a ridiculous thing to say."

Kate laughed. "RIDICULOUS is you making out with my witness over her father's dead body." She ignored Zara's reactive sob to the word "dead".

"Making out?" Castle thundered; his hands immediately at his hips. "Making OUT? If you think THAT was making out, then I have really got to…" He let the thought trail off, turning back to glance at Zara.

Kate scanned the blonde's slender form, taking note of the wisps of hair stuck to her cheeks by her tears, the redness of her throat; her hands shaking as she wiped the blood from them on a cloth Rick must have handed her. On the third finger of her left hand was a ring. Kate couldn't tell from her current vantage point what the material was – too white to be gold, too luminous to be platinum. It formed a delicate knot over the top of her slender finger as Zara half-heartedly cleaned it.

"Miss Chase," Kate said quietly.

"Zara," the blonde answered, her voice devoid of emotion. "My name is Zara."

"Zara," Kate repeated with an annoyed tone that made Rick unconsciously roll his eyes. "My detectives say you found your father?"

She sniffed and closed her eyes tight as another sob threatened to erupt. "Yes, he, uh, wanted to meet with me. I punched the button for the elevator from the lobby and I heard what sounded like a…" Zara began to hyperventilate and Rick was behind her in flash, his arms wrapped protectively around her shoulders.

"A gunshot," she continued, seemingly reassured by Rick's touch. "I dropped my bags and took the stairs. I got to the door of the study and he was lying there…there was so much blood. I felt for a pulse…and…and…there was no pulse." Her anguished tone had Rick burying his face in her hair. "I called 911, and then started CPR, and…"

Zara was cut off by another familiar voice in the hallway, yelling at the uniformed officer to "get the hell out of my way." Ryan pushed the door open and was nearly overrun by Castle's mother, Martha.

The blonde lept from the chair and into Martha's arms. "My baby," Martha cried, "my sweet baby girl, I am so sorry…"

Kate's confusion was suddenly compounded. Baby girl? Richard Castle was an only child.

"Oh God, Mom…" Zara said quietly, clinging desperately to the older woman.

Kate looked to Castle for clarification. He swallowed hard and looked at her with tears in his eyes. "Zara is, uh, my little sister."


	2. Chapter 2

Disclaimer – I don't own Castle or any of the characters. Although I will admit wishing I DID own Castle after the picture of NF that was on the website from Comic-Con. He really IS ruggedly handsome!

"Zara is, uh, my little sister."

Kate stared incredulously at Rick before grabbing his elbow and dragging him out of the kitchen. "Your _sister?" _she repeated slowly. "You don't HAVE a sister, Rick."

Castle shrugged and glanced back at his mother and Zara through the small round window in the swinging door. "You're half right," he answered. "Richard Castle is an only child. Richard _Rodgers_...not so much."

Ryan poked his head cautiously through the door and poked his thumb back over his shoulder. "Hey Beckett, Martha is asking if Zara can change her sweater since it's covered in blood. Techs found her bag downstairs in the lobby."

Kate's eyes never left Rick's as she answered "Fine. Have them bag the clothes and the towel she wiped her hands on. We'll need to test for GSR."

The fire behind Castle's eyes startled her. "Are you KIDDING me?" he yelled. "Gun shot residue? You seriously think she shot Conrad?"

"Castle, I don't know what the hell to think right now," she shot back angrily. "First, you freak out when I tell you where we're going, then you take off like a bat out of hell up the stairs and I find a woman covered in blood in your arms and you're telling me she's some sister you've never bothered to mention in the four years we've worked together. Forgive me for being just a little confused."

Rick took a deep breath and ran a hand through his hair. "I'm sorry, Kate."

A crime scene tech interrupted them with Zara's bag. "She's in there," Kate said quickly. "Ryan will tell you what I need."

The tech nodded and started through the swinging door. Rick glanced in to check again on his mother and sister. "She didn't kill Conrad," Castle said after the tech disappeared into the kitchen. "No way. First of all, she has absolutely no reason to kill her father, and even if she did, did you SEE her? Why would she be that distraught?"

Kate rolled her eyes. "Guilt, maybe?"

"No," Castle said again with a furious shake of his head. Kate both loved and hated the overprotective streak that reared its head anytime she, Martha, Alexis, or now, presumably Zara, were in trouble. She appreciated his loyalty but despised how it prevented him from thinking with his head.

Rick suddenly snapped his fingers. "Cameras! Conrad had security cameras. I...I know the lobby is covered, or...at least it used to be. The stairs too, and the foyer."

He took off again for the stairs leading to the second level. "The command center for the security system was in the master bedroom closet."

"Castle!" Kate yelled after him. "We'll send the techs to take a look. YOU cannot be up there."

"What? Why not?" His face registered disbelief.

"Oh my God, Castle, conflict of interest? Your...I don't know what the hell he was to you, stepfather, is dead and your sister is, at the moment, a suspect."

Martha emerged from the kitchen looking suddenly much older than when she'd arrived and first taken Zara into her arms. "Kate, darling, is there someplace we can talk?" the older woman asked gently.

"Uh, yeah," Kate answered, somewhat startled. She stuck her head back in the kitchen and noticed Zara at the table again, clad in clean white button down shirt, sipping a cup of tea. "Esposito, I need you to keep Castle in the kitchen. Do NOT let him out of your sight."

Martha led Kate into a room opposite where Conrad Chase's body still lay in his study. It was a music room, flanked on each end by a grand piano and an ornate fireplace. Martha picked up a framed photo from a table near a small couch, glanced at it, smiled and held it to her heart before handing it to Kate.

She couldn't help but smile at the faces staring back at her. A very young Richard Rodgers and Zara Chase, sitting at the piano still in the corner of the room, with four hands on the keys, laughing as only young children can do.

"Richard was eight when Conrad and I married. Zara was barely four. Her mother had been killed in a car accident when Zara was less than a year old. Richard had always wanted a sibling and when he finally got one," Martha laughed, "he didn't waste a minute turning into a classic, stereotypical, overprotective big brother.

"They were inseparable," she sighed, gently turning the page on a music book propped against the piano. "I look around this house and I swear I can still hear their laughter. I can see them playing hide and seek."

Kate followed Martha's gaze back into the foyer, allowing herself for just a moment to imagine the young boy in the picture, with his sandy brown hair and eyes full of mischief chasing a petite blonde pigtailed little girl.

"How long were you married?" Kate inquired, snapping Martha from her memories.

"A little more than seven years," she answered. "Seven of the happiest years of my life. Well, until I caught him in his office with his secretary bent over his desk. After that, _I _wanted him dead."

Martha sucked in a gasp and covered her face with her hands. "I should not have said that," she said apologetically.

"Would Zara have any reason to kill her father?" Kate inquired.

Martha shook her head. "Conrad was not the easiest man to love, especially after the divorce. He tried so hard to cut me off from Zara after I sued for joint custody. She resented him for that."

"Enough to put a bullet in his head?" Kate continued.

"Absolutely NOT," Martha answered emphatically. "I've always been a part of Zara's life, thanks to some very understanding nannies."

"Rick has never mentioned her," Beckett said quietly.

Martha laughed bitterly. "That would be Conrad's doing. When he found out Richard was having a book published, he filed an injunction to prevent Richard from mentioning Zara in the acknowledgements."

"How did Castle feel about that?" Kate asked curiously.

Martha sighed. "He was angry. I was angry, so was Zara. Conrad hated to lose. It's one of the reasons he was so successful."

"Did Conrad have any enemies that you know of?"

"Of course he did. You don't get to his level of success without burning a few bridges and stepping on a few toes. You should be able to get a fairly accurate list from his assistant."

Martha took a deep breath and glanced out into the foyer before continuing. "There's something else, Kate, something the children have no idea about."


	3. Chapter 3

First of all, let me say thank you to everyone who has read and reviewed this story. I apologize for the delay in updating – I didn't get as much alone time on my trip as I thought I would!

Martha took a deep breath and glanced out into the foyer before continuing. "There's something else, Kate, something the children have no idea about. Three weeks ago, Conrad called me, said he wanted to see me and begged me not to tell Richard."

Kate stepped closer to Martha as the elder woman's voice became little more than a whisper. "Conrad was dying. Brain cancer. He only had a few weeks left according to the doctors and he wanted to make amends. We had a wonderful visit. His next calls were going to be to Richard and Zara."

"And they had no idea?"

Martha shook her head again. "As far as I know, Conrad hadn't yet called Richard. He hasn't said anything to me if he has."

"What about Zara?"

Martha shrugged. "He must have called her - she's _here_."

Kate bit the inside of her bottom lip as she processed the new information. "Okay," she said finally, "thanks, Martha."

"Kate," Martha said quietly, "if there is anyway you could let me tell Richard and Zara about Conrad.."

"I'll do my best," Kate said with a small, reassuring smile.

She returned to the kitchen door, steeling herself momentarily against the intense waves of emotion she'd felt since beginning this case with a deep, cleansing breath. She only wished that had been enough.

Rick was at the table, his hand over Zara's, unconsciously rubbing small circles on her hand with his thumb. Kate's breath hitched in her chest. That was how she'd woken up from surgery after being shot – with Rick's hand holding hers. She swallowed the surge of jealousy that suddenly consumed her and pulled out a chair at the table, sitting down directly across from Castle.

"Zara," she began quietly. "I need to ask you a few questions."

"Do you really have to do this _now_?" Rick asked, his tone irritated.

She shot him a steely glare. "Yes, Rick, I have to do this _now_."

Zara squeezed his hand and gave him a sad smile. "It's okay, Rick, really."

Castle finally tore his eyes from Kate's and shook his head.

"Where were you flying in from, exactly?" Kate asked.

"Haiti," Zara answered. "I've been running a medical clinic there since the earthquake."

"You're a doctor?"

Zara nodded. "Internal Medicine, Johns Hopkins."

Kate eyed the blonde with a new interest. "Doctors Without Borders?"

"No," Zara answered quickly. "It's a private clinic run by private funding, my inheritance and profits from my father's endeavors. There are 8 clinics in various locations throughout the world. My primary focus has been Haiti, though."

"What brought you back to New York?"

"My father."

Kate's eyebrows raised as she waited for Zara to complete the thought. She didn't.

"What about your father?" she prodded, anxious to know if Zara was aware of her father's condition.

Kate watched intently – seeing the wheels turn in Zara's brain as her mood suddenly shifted. She took a deep breath and blew it out slowly. Kate noticed Rick's fingers tighten over Zara's as she began to answer.

"My father..." she started slowly, "threatened to cut off my funding for the clinics."

Beckett's eyes went wide. "I bet that made you angry."

Zara laughed bitterly. "Not enough to _kill_ him, Detective Beckett."

"You sure about that?" she challenged.

Rick was out of his chair, stalking around the side of the table at Kate's question. He grabbed her arm, nearly yanking her out of her chair.

"Beckett, a word?"

"Let go of me, Castle," Kate warned through clenched teeth.

She saw an apologetic flash in his eyes before anger took over again. He dropped his hand from her arm and pushed the kitchen door open with such force it slammed against the plastered wall behind it.

Castle waited for the door to close fully before beginning to speak. "She did NOT kill him, Kate. What part of that don't you understand?"

Kate fought the urge to laugh in his face. "He threatened to cut off the funding for her medical clinics, Rick. I'd say that's one hell of a motive."

"Oh please," Castle shot back. "This isn't anywhere near the first time Conrad has pulled that. He threatens to cut off her funding constantly."

"So, you're telling me Zara and Conrad had a contentious relationship?"

The fire of anger in Rick's eyes suddenly burned brighter, startling Kate. "Yes, Kate, they had a contentious relationship," he answered sarcastically. "Conrad even had a contentious relationship with himself."

"Why would he threaten to cut off her funding?"

Castle ran a hand through his hair before crossing his arms over his chest. "Conrad was a difficult man, but he loved Zara. He just..." Rick closed his eyes and sighed heavily.

"He what, Rick?" she prodded.

"Didn't know how to have a healthy relationship with her. She gets so caught up in the clinics that sometimes we don't hear from her for months on end. Mother and I leave messages where we can and know she'll call us back eventually, but Conrad isn't a patient man. When he wanted to see her, or talk to her, he wanted it right that second. In his warped mind, threatening to cut off her funding is a great way to get her home quickly."

"Maybe Zara got tired of the threats?"

Rick shook his head. "She knew exactly what he was doing. After the first three times he made the threat, she finally stopped taking him seriously. She'd come home for a couple of days, do her song and dance with Conrad and the Board of Directors, and then she'd go back to wherever with all of her funding in tact, and then some."

"She admitted it made her angry."

Castle rolled his eyes. "It was more of an irritation than anything. She didn't like having to leave her patients just to soothe him."

Kate bit her bottom lip again and looked seriously at her partner. "Rick," she said quietly. "So far you haven't told me one thing that actually helps your sister. She has a lot of motive."

Rick turned to the wall and slammed his fist into it before turning back to glare at Kate. "Fine. But if you're going to treat my sister as a suspect, you might as well treat me like one too. I have just as much motive to kill him as she does."


	4. Chapter 4

Disclaimer – still don't own Castle but still wish I did!

* * *

><p>Rick's words rolled in her mind over and over – like a tide that simply would not stop. "I have just as much motive to kill him..." She twisted her gold chain with her finger and bit the inside of her bottom lip, a bad habit she couldn't remember when she'd picked up. She was leaned back in her chair, staring across the desk to the empty chair across from her – the one always occupied by Castle. She'd lost count of how many times in the last 48 hours she'd looked up to say something to him, only to find him not there.<p>

She tried to shake the image of his face from her mind – how hurt he'd looked when she ordered him away from the crime scene. She couldn't help but feel like she'd betrayed him, but she had a job to do and he certainly was not aiding her investigation.

Lost in her own thoughts, she unconsciously took a sip of the coffee that had suddenly materialized on her desk before she realized she wasn't alone. "Castle, you can't be here."

Rick sat down on the edge of her desk and looked down at her. "I know, Kate, I'm only going to stay a minute. I just wanted to apologize."

She glanced up at him and swallowed a sob. He truly looked awful. Dark bags circled his eyes and the weight of the last two days sagged his shoulders. "It was...presumptuous...of me to expect my word to be enough for you not to suspect my sister. I'm sorry for that. I'm sorry for my anger. It wasn't really directed at you, it was the situation."

She smiled softly at him. "I appreciate that, Rick."

He shook his head. "I'm not finished. I'm sorry I didn't tell you about Zara. I've racked my brain trying to remember why I never told you I have a sister. I guess...I don't know, I thought you knew, or I assumed you did, or maybe I just expected you to know..."

Ryan interrupted Rick's confession with an apologetic glance at both of them. "GSR test are back." He handed the file to Beckett as Castle shifted his weight uncomfortably.

She opened the file and quickly read the results; then, offered her partner a small smile. "Zara's clothes were clear." Rick's eyes closed involuntarily as relief flooded over him. "Only a trace amount on her hands, most likely from her performing CPR on Chase."

"I _told_ you she didn't kill him," Castle said triumphantly. "What about the security cameras? Did they show the killer?"

Kate laughed gently. "Castle, you know I can't talk about the case with you. You're entirely too close to this one."

Rick nod his head. "I know, I'm sorry."

She offered him a brilliant grin. "You can _seriously_ stop saying you're sorry now."

"I'm sorry," he said quickly.

"Castle!"

He mimed zipping his lips and tossing the key. Kate rolled her eyes. Ryan laughed and shook his head at his colleagues. "I have more," he announced, "if you're cool with Castle hearing it."

Rick look so jubilant at the GSR results, she found herself unable to say no. "Knock yourself out," she answered.

"The security tapes," he began, shooting Castle one of their many hand gestures, which was quickly returned, "didn't show any perps, which is bad news for us. But, it did confirm Zara's timeline exactly, which is good news for..."

"Me," Castle interrupted. Ryan nod in agreement.

"Security feed recorded Zara Chase enter the building's lobby at 10:36 p.m two nights ago. The cameras don't have audio, but it clearly shows her pressing the button for the elevator, reacting to something seconds later, dropping her bags and running out of frame. Stairwell cameras picked her up immediately after. There are cameras in the foyer of the residence part of the building, but not in the living quarters."

"Anyone else seen entering or leaving the building?" Kate asked curiously.

Ryan pulled a photo from the file in his hand. "Cameras picked up this lady leaving at 8:04 p.m." Kate glanced at the photo before handing it to Castle. He shook his head, indicating he'd never met the woman in the photo. "According to Chase Enterprises website, the woman is Natalie Benson, Chase's executive assistant. After Zara, the next people on the feed were our unis responding to the 911 call."

"Natalie have a reason for leaving that late in the day?" Kate asked.

"She said that was actually an early night for her. Working for Conrad Chase was a 24/7/365 job."

"_That_ I can attest to," Rick offered. "The man worked more than anyone I'd ever met and kept his employees on very short leashes, especially his assistants."

"She give you anything else – a list of people Chase had pissed off recently?"

Ryan shook his head. "She said that the last 2 months have been unusually quiet and that Chase had been out of the office more than usual and just generally acting strange."

"Probably the cancer," Rick offered.

Kate's eyes went wide with shock. "You know?"

Castle nodded his head. "Mother told Zara and I later that night. She is very appreciative to you for allowing her to be the one to tell us."

"That's something that probably needed to come from a parent, not some random homicide detective," Kate responded with a shrug.

"You're _not_ a random homicide detective, Kate. Not to me."

She quickly looked away, praying her reaction went unnoticed by Castle. She'd heard his declaration of love for her before she surrendered to the sweet serenity of unconsciousness after she'd been shot. He was by her side almost the entire time she was in the hospital recovering and paid for a private nurse when she'd insisted on going home but refused the offer to stay at his place. For some reason she still couldn't put her finger on, she couldn't force herself to acknowledge Rick's confession, though she desperately wanted to.

"Any other way in or out of the living quarters?" she asked, effectively changing the subject.

Before Ryan could answer, Castle said, "yeah, there's a door that leads to the garage through the butler's pantry, off the kitchen. It's how I would sneak out of the house when I was 14. Conrad only has cameras in the common areas of the house, not the private rooms. When I was a kid, there was only one camera in the garage. If you stayed flat against the wall, you could make it to the door without the camera picking you up...and why are you grinning?" he asked Kate curiously.

She laughed. "Sorry, just the image of you at 14 sneaking out of the house."

"I was not always the bastion of honor, goodness and morality that I am today Mademoiselle," he countered sarcastically.

"And lemme guess, sneaking out might have had something to do with you landing in boarding school?" Kate asked with a grin.

Rick shrugged his shoulders. "I can neither confirm nor deny that accusation, Detective."

Kate laughed again and returned her attention to Ryan. "Any cameras in the garage?"

The younger detective sorted through the file and notes quickly. "Uh, there's nothing in here about a feed from the garage."

"And?" Kate prodded.

"Aanndd...I am going to go back to the guys with the system's server and find out for you..." Ryan answered before quickly retreating down the hall.

The silence left between Kate and Rick at Ryan's disappearance quickly became uncomfortable. Rick spoke first. "I should go...Zara wants to speak to Conrad's doctors about the cancer..."

"Yeah," Kate agreed, righting her chair and pretending to find interest in a report on her desk. She glanced up at him again. "I'm sorry, Rick."

Castle's eyebrows furrowed in confusion. "Why are you sorry?"

Kate shrugged. "I'm just sorry for what you and Martha and Zara are going through."

"Thanks," Rick answered softly. They exchanged smiles and barely whispered goodbyes before Castle turned to head out of the precinct.

"Hey Castle?" Kate asked loudly, just remembering something she needed to ask him. He turned and faced her again. "Yeah?" he answered.

"I noticed a ring on Zara's hand the other night. Is she married?"

Castle shook his head. "No, she said it's an engagement ring. Ivory, from Zimbabwe, where one of the clinics is located."

"You know the guy?"

"No," he answered easily. "Haven't met him yet. Zara said he's coming in to help her with the arrangements and the foundation affairs."

"He's in the clinic with her?" she continued.

"Yeah, she said he's back and forth between the clinics and the states a lot. I think his name is David or maybe Davidson."

Kate's breath caught in her throat and a sick feeling began to develop in the pit of her stomach. "Davidson the first name or last name?" she asked, not really wanting the answer.

"Uh...first...name...I guess." Castle studied his partner's stricken appearance with worried eyes. Why would she have such a reaction to a name, he wondered. "Davidson is the only thing I've ever heard Zara call him."

"Okay, Castle, thanks," Kate said quickly, turning her back to him and rushing back to her desk.

"Kate?" he called after her.

She waved him off dismissively. "Thanks, Castle, I've got work to do."


End file.
